This application claims the benefit of Korean Patent Application No. 2001-62947, filed Oct. 12, 2001, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a bubble-jet type ink-jet printhead, and more particularly, to a bubble-jet type ink-jet printhead having a recess formed on a substrate on which a bottom surface of an ink chamber is disposed.
2. Description of the Related Art
In general, ink-jet printheads are devices printing in a predetermined color image by ejecting a small volume of a droplet of printing ink at a desired position on a recording sheet. Ink ejection mechanisms of an ink-jet printer are largely categorized into two different types: an electro-thermal transducer type (bubble-jet type) in which a heat source is employed to form a bubble in ink to cause the ink to be ejected, and an electro-mechanical transducer type in which ink is ejected by a change in ink volume due to deformation of a piezoelectric element.
In the above-mentioned ink-jet printheads, ink is supplied to an ink chamber from an ink reservoir through an ink passage. Ink filled in the ink chamber is heated by a heating element in the ink chamber and is ejected in a droplet shape through a nozzle by a pressure of the bubble generated by the heating element.
FIG. 1 is a schematic perspective view illustrating a structure of a conventional bubble-jet type ink-jet printhead, and FIG. 2 is a cross-sectional view illustrating the conventional bubble-jet type ink-jet printhead shown in FIG. 1.
Referring to FIG. 1, the conventional bubble-jet type ink-jet printhead includes a base plate 10 formed of several different material layers stacked on a substrate 11 of FIG. 2, a barrier wall 20 which is stacked on the base plate 10 and defines an ink chamber 22 and an ink passage 26, and a nozzle plate 30 stacked on the barrier wall 20. The ink chamber 22 is filled with ink, and a heater (13 of FIG. 2) which generates the bubble in the ink by heating the ink, is provided under a bottom surface 24 of the ink chamber 22. The ink passage 26 is a path for supplying ink to the ink chamber 22 and is connected to an ink reservoir (not shown). A plurality of nozzles 32 through which ink is ejected, is formed at a location corresponding to a center of the ink chamber 22 on the nozzle plate 30.
Referring to FIG. 2, the conventional bubble-jet type ink-jet printhead having the above structure of FIG. 1 includes an adiabatic layer 12 which prevents a thermal energy generated by a heater 13 from being discharged toward the substrate 11, is formed on the substrate 11 formed of silicon. The adiabatic layer 12 is generally formed of a silicon oxide layer deposited on the substrate 11. The heater 13 which generates the bubble in the ink by heating the ink in the ink chamber 22, is formed on the adiabatic layer 12. The heater 13 is deposited by sputtering a tantalum-aluminum alloy in a thin film shape, for example. A conductor 14 transmitting a current to the heater 13 is formed on the heater 13. The conductor 14 is formed of an aluminum-copper alloy, for example.
Passivation layers 15a and 15b for passivating the heater 13 and the conductor 14 are formed on the heater thin film 13 and the conductor 14. The passivation layers 15a and 15b prevent the heater 13 and the conductor 14 from oxidizing or directly contacting ink and are formed of two layers, such as a first passivation layer 15a formed of a silicon nitride layer and a second passivation layer 15b formed of a silicon carbide layer. An anticavitation layer 16 is formed on the second passivation layer 15b where the ink chamber 22 is formed. The anticavitation layer 16 prevents the heater 13 from being damaged by a high atmospheric pressure generated when the bubble in the ink chamber 22 is removed, by forming the bottom surface 24 of the ink chamber 22 on an upper side of the anticavitation layer 16, and a tantalum thin film is generally used for the anticavitation layer 16.
The barrier wall 20 defines the ink chamber 22 and the ink passage 26 and is stacked on the base plate 10 that is formed of several different layers stacked on the substrate 11. The barrier wall 20 is coated through lamination for heating, pressurizing, and compressing a photosensitive polymer on the base plate 10, followed by patterning. In this case, a coating thickness of the photosensitive polymer is about between 25 xcexcm and 35 xcexcm and is determined by a height of the ink chamber 22 required by a volume of the ink droplet ejected.
The nozzle plate 30 on which the plurality of nozzles 32 are formed, is stacked on the barrier wall 20. The nozzle plate 30 is formed of polyimide or nickel and is heated and pressurized on the barrier wall 20 and attached to the barrier wall 20 using adhesion of the photosensitive polymer forming the barrier wall 20.
In the above structure of the conventional bubble-jet type ink-jet printhead, the photosensitive polymer forming the barrier wall 20 is used to attach the base plate 10 to the nozzle plate 30 and surrounds the ink chamber 22. Ink filled in the ink chamber 22 contains water of about between 60% and 70%, and water soaks not only into an adhesion interface among the base plate 10, the barrier wall 20, and the nozzle plate 30 but also into the photosensitive polymer forming the barrier wall 20. This phenomenon causes the delamination between elements of the ink-jet printhead and thus is a main factor in causing a defect of the ink-jet printhead.
Also, a crosstalk that affects the formation of bubbles and ejection characteristics of ink due to an atmospheric pressure applied to the adjacent ink chamber 22 through the ink passage 26 during ink ejection, may occur easily.
Also, the nozzle plate 30 adheres to the barrier wall 20 after the barrier wall 20 is formed on the base plate 10. Hence, if the height of the barrier wall 20 is large, the barrier wall 20 may be easily deformed when the nozzle plate 30 is heated and pressurized on the barrier wall 20 to be attached to the barrier wall 20. As a result, a misalignment among the nozzle 32, the ink chamber 22, and the heater 13 occurs, and thus results in poor performances of the ink-jet printhead.
To solve the above and other problems, it is an object of the present invention to provide a bubble-jet type ink-jet printhead which prevents delamination and improves ejection characteristics of ink droplets by reducing a height of a barrier wall of an ink chamber by forming a recess on a substrate on which a bottom surface of an ink chamber is disposed.
Additional objects and advantageous of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Accordingly, to achieve the above and other objects, there is provided an ink-jet printhead. The ink-jet printhead includes a base plate including a substrate on which a recess is formed to a predetermined depth, an adiabatic layer formed on the substrate, a heater which is formed on the adiabatic layer and generates a thermal energy, and a passivation layer which is formed on the heater and passivates the heater, a barrier wall which is stacked on the base plate and defines an ink chamber disposed on the recess and having a recessed bottom surface and an ink passage which communicates with the ink chamber, and a nozzle plate stacked on the barrier wall and having nozzles through which ink is ejected, formed at a location corresponding to a center of the ink chamber.
Here, the recess is formed by wet or dry etching a predetermined surface of the substrate on which the ink chamber is to be formed, and a depth of the recess is between 1 xcexcm and 20 xcexcm, preferably, between 5 xcexcm and 15 xcexcm.
It is possible that the adiabatic layer is formed of a silicon oxide layer formed by oxidizing the surface of the substrate, and a thickness of the silicon oxide layer is between 1 xcexcm and 5 xcexcm.
It is also possible that the heater is formed of a tantalum-aluminum alloy or polysilicon, and a thickness of the heater is between 500 xc3x85 and 5,000 xc3x85.
It is also possible that the passivation layer is formed of a silicon nitride layer deposited on the heater or two layers of a silicon nitride layer and a silicon carbide layer, which are sequentially deposited on the heater.
It is also possible that an anticavitation layer which prevents damage of the heater, is formed on the passivation layer, and that the anticavitation layer is formed of a tantalum layer.
Here, it is possible that a thickness of each of the silicon nitride layer, the silicon carbide layer, and the tantalum layer is between 0.1 xcexcm and 1.0 xcexcm inclusive.
Meanwhile, the barrier wall is formed of photosensitive polymer by a photolithography process. The photosensitive polymer is formed in a dry film shape and is coated on the base plate through lamination. The photosensitive polymer is coated to a thickness of between 5 xcexcm and 24 xcexcm on the base plate.
In addition, the nozzle plate is formed of polyimide or nickel.
According to the embodiment of the present invention, the height of the barrier wall surrounding the ink chamber is reduced more by forming the recess formed on the substrate, and thus delamination that occurs by ink soaked into the barrier wall, is prevented, and print performances, such as a traveling property in a straight direction of ink droplets and ejection velocity of ink droplets, are improved.